Wind turbines are increasingly used for the generation of electrical energy. A wind turbine typically comprises a rotor-driven turbine generator mounted atop a tower constructed of multiple tower sections that are stacked and secured together. It is common for wind turbine components such as the tower sections to be transported on shipping vessels to their desired destinations.
Certain cargo shipping vessels have weather decks that are equipped with accessible locking mechanisms such as conventionally known semi-automatic twist-lock mechanisms for releasably securing conventional cargo containers (e.g., rectangular, box-shapes cargo containers) to the weather decks. The cargo containers have corresponding locking mechanisms at their bottom corners for mating with the locking mechanisms on the deck, and at their top corners to lock together stacked cargo containers. The ship's locking mechanisms are thus spaced across the width of the deck and located intermittently longitudinally of the deck.
For shipping purposes, wind turbine tower sections—which are typically cylindrical or frusto-conical—are fitted at both ends with a support member having a bottom that defines a pair of spaced apart feet or a straight, flat surface for stably resting the tower section on the ship's deck and for preventing the tower section from rolling. Additional locking mechanisms may be located at the top of the support member to permit stacking (in side-by-side relationship) of tower sections in the same manner as a cargo container.
The support frames at the ends of the tower sections are often welded to the deck because the spacing of locking mechanisms across the width of the deck is not standard among ships because tower sections come in different cross-sectional dimensions (e.g., diameters). Additionally, the wind turbine tower sections are typically larger (e.g., in diameter) than cargo containers, making it difficult to align the feet of the support members with the ship's locking mechanisms. The welding takes place during loading and unloading of the sections. This welding and unwelding, however, is time-consuming and expensive.
Additionally, some shipping vessels that are used to transport wind turbine tower sections have decks or floors with a maximum pressure rating of 2.5 metric tons per square meter. As larger and larger wind turbine tower sections are being used and transported, the weight of the sections that are transported on shipping vessels is increasing and the pressure they exert on the decks and floors of shipping vessels is increasing. While it would be desirable to increase the number of tower sections that can be loaded across the width of the ship's weather deck, it is important to heed the load limits of the deck. There is a need, therefore, for a system and/or method of shipping wind turbine tower sections that permits an increased number of tower sections to be transported on a shipping vessel.